While Mohs Micrographic Surgery has long served as the method of choice for treatment of nonmelanoma skin cancer, current techniques require timely tissue processing methods resulting in procedures that can last from several hours to an entire day. In order to improve upon the tools that are currently available to dermatologic surgeons to accurately assess tumor margins, a real-time evaluation technique is needed. To overcome the limitations currently faced for rapid evaluation of tumor margins in Mohs surgery, spatially offset Raman spectroscopy (SORS) is proposed. Raman spectroscopy an optical technique that probes the vibrational energy transitions of molecules upon their interaction with light. The resulting Raman spectrum contains signature peaks that can be associated with a particular chemical bond or a functional group in a molecule yielding structural and environmental information. SORS is based upon the inelastic light scattering of chemical bonds intrinsic to molecules, but has the capacity for the biochemical specificity with added depth selectivity necessary for surgical guidance and margin evaluation. SORS has been applied in a number of tissues, collecting spectral information from up to millimeters in depth, as needed for the proposed application. The overall goal of this research is to provide a tool for guidance, monitoring surgical performance and long term follow-up of Mohs patients in situ. Further, this application seeks to evaluate the capability of SORS to evaluate surgical margins regardless of the patient demographics, history, or disease manifestation. The specific aims are thus proposed: (1) Characterize cutaneous malignancies in vivo using Raman spectroscopy during Mohs surgery, to identify malignant and normal tissues based on Raman bands for a discrimination and classification algorithm necessary for real-time, automated margin evaluation; (2) Model and develop a SORS probe for margin assessment and guidance, differentiating soft tissue layers by comparing modeling and experimental results for optimized performance; and (3) Probe validation in (a) phantom, (b) excised skin sample, and (c) pilot study to evaluate performance in vivo during Mohs surgery. Through complimentary studies utilizing a combination of controlled phantom and actual clinical samples, the SORS probe and real-time discrimination algorithm to determine the predictive probability of accurately classifyin samples with positive and negative margins will be evaluated. It is anticipated that successful monitoring of margin evaluation will be accomplished with SORS guidance for Mohs with increased speed and efficiency. While the ultimate goal of SORS from a clinical perspective is to decrease procedural time and increase patient throughput, demonstrating the capabilities of SORS as a guidance and margin evaluation adjunct is a necessary initial step. In addition to experience provided by the research project, the proposed research training plan aims to supplement the research development through coursework, peer review, expert mentoring, networking, manuscript submission, and participation in scientific meetings and seminars.